Functionalization of polymers is often desirable to meet a particular manufacturing need. For example, polymers may be functionalized to improve toughness, enhance the acceptance of flame retardants, mineral stiffeners, glass or wood fibers, or other desired ingredients. Polymers may also be modified to help them combine more usefully or deliver higher value when recycled. Modifications can improve wetting, aid mix dispersion, filler adhesion, melt processing, surface-to-surface attraction, and other performance features. Such polymers are of interest for use in a broad range of applications as lubricants, compatibilizers, tie-layer modifiers, surfactants, and surface modifiers, among other things.
Methods for the production of polyolefins with end-functionalized groups are, however, typically multi-step processes that often create unwanted by-products and waste reactants and energy. However, metathesis has been used to functionalize polyolefins in a single step with some success.
Metathesis is generally thought of as the interchange of radicals between two compounds during a chemical reaction. There are several varieties of metathesis reactions, such as ring opening metathesis, acyclic diene metathesis, ring closing metathesis, and cross metathesis. For example, R. T. Mathers and G. W. Coates, Chem. Commun., 2004, pp. 422-423 disclose examples of using cross-metathesis to functionalize polyolefins containing pendant vinyl groups to form polar-functionalized products with a graft-type structure.
Additionally, some reviews of methods to form end-functionalized polyolefins are: (a) S. B. Amin and T. J. Marks, Angew. Chem. Int. Ed., 2008, 47, pp. 2006-2025; (b) T. C. Chung, Prog. Polym. Sci., 2002, 27, pp. 39-85; and (c) R. G. Lopez, F. D'Agosto, C. Boisson, Prog. Polym. Sci., 2007, 32, pp. 419-454. Even further, U.S. Ser. No. 12/488,093, filed Jun. 19, 2009, discloses end functionalized polyolefins prepared from vinyl terminated polyolefins by cross-metathesis.
A variation on ring-opening metathesis polymerization, which has to date been the subject of only limited research, is ring-open cross metathesis (ROCM). ROCM involves a tandem sequence in which a cycloolefin is opened and a second, acyclic olefin is then crossed onto the newly formed termini. For example, U.S. Pat. No. 6,803,429 discloses that certain Group 8 metal alkylidene complexes substituted with N-heterocyclic carbine ligands catalyze the ring-opening cross-metathesis of cycloolefins with acyclic olefinic reactants, particularly α,β-unsaturated carbonyl compounds. The ROCM products are said to be mainly monomeric, dimeric, or oligomeric species, rather than polymers.
Likewise, U.S. 2008/0064891 discloses ROCM reaction of cyclic olefins with seed oils and the like comprising contacting: (a) at least one olefinic substrate selected from (i) an unsaturated fatty acid, (ii) an unsaturated fatty alcohol, (iii) an esterification product of an unsaturated fatty acid with an alcohol, and (iv) an esterification product of a saturated fatty acid with an unsaturated alcohol; with (b) at least one cyclic olefin as a cross-metathesis partner; in the presence of (c) a ruthenium alkylidene olefin metathesis catalyst; and (d) under conditions effective to allow ring insertion cross-metathesis whereby the cyclic olefin is simultaneously opened and inserted into the olefinic substrate.
Further, WO 98/40373 discloses ROCM on solid supports to isolate the olefin immobilized on the resin, preventing unwanted olefin polymerization. Additional references of interest include: U.S. Pat. Nos. 4,988,764; 6,225,432; EP 1 693 357; U.S. Ser. No. 12/487,739; and U.S. Ser. No. 12/143,663.
In summary, there is a need to develop a means to provide functionalized polyolefins (particularly end-functionalized polyolefins) by metathesis reactions, particularly reactions with good conversion, preferably under mild reaction conditions with a minimal number of steps.